Although the present invention finds utility in a variety of applications, it is intended primarily for use in conjunction with electrophotographic duplicating apparatus for the purpose of providing a storage facility for the masters which such apparatus generates and discards.
Typically, the electrophotographic duplicating apparatus with which this invention is primarily concerned comprises essentially two major components, an electrophotographic copying component which generates a master copy from an original document, and a lithographic press component which utilizes the master to produce ink copies of the original document from the master. The master is produced in the copying component in the typical manner well known in the electrophotographic art, that is, by projecting an image of the original document onto a photoconductive surface of the master which surface has been uniformly electrostatically charged, and then developing the charage image pattern left on the photoconductive surface of the master sheet after exposure thereof to the image projection from the original document by deposition of electrostatically attractible toner particles. The master thus produced is a graphic reproduction of the original document, and would itself constitute a usable copy were it not for the special paper on which this copy is made which is primarily intended for lithographic reproduction. The master is now chemically treated in a known manner so as to render the image areas thereof oleophilic and the background areas thereof hydrophilic so that the image areas will accept lithographic ink but the background areas will not accept the ink.
The master is placed upon a printing drum of the lithographic press component and ink is applied thereto in a manner known in the lithographic press art. Thereafter, sheets of ordinary copy paper are successively fed into the lithographic press and ink is transferred from the image areas of the master to the copy paper to produce the ultimate copies of the original document. The ink may be transferred from the master to the copy paper either directly or through the intermediary of an offset or blanket roll, both of which procedures are well known in the art.
In the type of duplicating apparatus with which the present invention is concerned, the foregoing steps of producing the master in the copying component and utilizing the master in the press component are carried out either semi-automatically or completely automatically. That is, the master can be manually taken from the copying component and inserted into the press component, with the chemical treatment being accomplished in the copying component, in the press component or in between the two. Alternatively, a transfer mechanism can be provided which will take the master from the copying component and transfer it to the press component. In either event, it is typical in apparatus of this type that the master is automatically received by and clamped to the printing cylinder on which the master is wound during a printing operation, and the master is automatically released by and stripped from the printing cylinder when the desired number of ink copies have been produced. The used master is then discarded and a new master comes into operation on the press component.
Until the development of the present invention, no completely satisfactory method or device had been devised for handling the used masters. Typically, the used masters are to some extent wet both from ink and from dampening solution which is used to maintain the background or non-image areas of the master free of ink, and accordingly the masters are rather messy for an operator to handle after being stripped from the printing cylinder. Also, the masters are rather limp in terms of the normal flexibility of paper which characteristic renders the masters difficult to handle by conventional paper handling devices. Still further, the masters typically have a tendency to curl after being discarded from the printing cylinder with the result that stacking of the masters in conventional stacking apparatus is not easily or efficiently achieved. All of these problems render the presently known ways of handling used masters relatively unsatisfactory, particularly in those situations where it is desired to make copies of a large number of original documents and a correspondingly large number of masters are generated during any given reproducing period of operation.